package net.vinote.smart.platform.module.security;

import java.security.MessageDigest;

public final class Md5
{
    private Md5()
    {
        
    }
    
    /**
     * 字符参数
     * @param s 字符参数
     * @return string 编码
     */
    public static String mD5(String s)
    {
        final int m = 2;
        final int n = 4;
        final int a = 0xf;
        char[] hexDigits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'a', 'b', 'c', 'd', 'e', 'f'};
        
        try
        {
            byte[] strTemp = s.getBytes();
            MessageDigest mdTemp = MessageDigest.getInstance("MD5");
            mdTemp.update(strTemp);
            byte[] md = mdTemp.digest();
            int j = md.length;
            char[] str = new char[j * m];
            int k = 0;
            byte byte0 = 0;
            for (int i = 0; i < j; i++)
            {
                byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> n & a];
                str[k++] = hexDigits[byte0 & a];
            }
            return new String(str);
        }
        catch (Exception e)
        {
            return null;
        }
    }
    
    /**
     * 获取16位的MD5密文
     * @param encryString 需要加密的字符串
     * @return 加密后的字符串
     */
    public static String bit16MD5(String encryString)
    {
        final int p = 9;
        final int q = 24;
        if (null == encryString)
        {
            return "";
        }
        else
        {
            String bit32 = Md5.mD5(encryString);
            return bit32.substring(p, q);
        }
    }
}